Method of rocket propulsion using liquid ammonia and ammonium perchlorate



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, 3,024,595 METHOD OF ROCKET PROPULSION USENG LIQUID AMMONIA AND AMMONIUM PER- CHLORATE Edward Phelps Helven's'ton and Thorowgood Taylor Broun, Jr., Corpus Christi, Tex, assignors, by mesne assignments, to Pittsburgh Plate Glass Company No Drawing. Filed Jan. 7, 1959, Ser. No. 785,312 2 Ciairns. (Cl. 60-35.4)

This invention relates to liquid fuels, particularly liquid fuels useful as rocket propellants.

Fuels with which the present invention is concerned possess in combination properties marking them as particularly suitable, even outstandingly superior, rocket propellants. Their specific impulses are of a magnitude denoting suitable, if not outstanding, usefulness as rocket propellants. Moreover, at normal temperatures these fuels are liquid compositions comprising both the oxidizer and fuel. Hence, they are liquid monopropellants. Considering their fuel properties, these liquid compositions are surprisingly stable. They may be stored or handled, for example, with convenience and a minimum danger from explosion, requiring neither pressure containers nor refrigeration.

Now it has been discovered that normally liquid compositions of ammonium perchlorate and ammonia having high ammonium perchlorate concentrations are useful fuels having the aforementioned advantageous properties. Thus, liquid compositions of ammonium perchlorate dissolved in anhydrous (or essentially anhydrous) ammonia, especially those which contain at least about 65 percent, prefer-ably up to 70 percent or about 80 percent, ammonium perchlorate by weight possess a most desirable combination of properties valuably exhibited by propellants. Accordingly, liquid compositions of ammonium perchlorate and ammonia are useful as fuels for propelling objects through space, especially rockets.

At temperatures of minus 40 C. to 50 (3., these compositions of ammonium perchlorate and ammonia are liquid and remarkedly stable (in view of their components); they evidence low vapor pressure. Because of this, they may be stored and handled with commendable ease; neither refrigeration nor the use of pressure containers being essential. By comparison with many other rocket propellants, they are easily handled or stored liquids. Moreover, they constitute a monopropellant since both a rocket oxidizer (ammonium perchlorate) and a rocket fuel (ammonia) are present.

Liquid compositions of ammonium perchlorate and ammonia containing upwardly of 65 percent by weight of ammonium perchlorate accordingly offer many advantages when used as a rocket propellant. When ammonium perchlorate and ammonia are present in stoichiometric proportions required for their combustion, the composition as such may be fed directly to the combustion chamber of a rocket or like propulsion device by suitable pumping or like means, being introduced into the chamber at a pressure consistent with the operational pressure in the combustion chamber.

If desirable, e.g., when the ammonia-ammonium perchlorate liquid compositions contain less than a stoichiometric amount of ammonium perchlorate, other oxidants such as oxygen, fluorine or the like may be employed to make up the deficiency of oxidant. Thus, such additional oxidant may be mixed with the compositions prior to their introduction into or within the combustion cham- An oxidant soluble in the liquid composition may Of course, a fuel other than ammonia which is soluble may also be included.

The advantages of a liquid fuel monopropellant of the type herein described for use in rocket engines or the like are many. One principal advantage is that the monopropellant requires but a single storage and feeding system. Multiple storage containers, complicated metering systems for proportioning oxidant and fuel and difficulties in metering gases are thus avoidable. By comparison with normally gaseous materials, these liquid compositions are easily stored, pressure storage and refrigeration being avoidable.

Liquid ammonium perchlorate-ammonia compositions here contemplated are prepared, for example, by dissolving ammonium perchlorate in liquid ammonia or by condensing ammonia on solid ammonium perchlorate crystals cooled to 0 C. Ammonium perchlorate may be added to liquid anhydrous ammonia, usually while the ammonia is under such pressure and/or temperatures at which it is liquid. After the perchlorate has dissolved, the resulting solution may be allowed to warm, generally to normal temperatures such as 20 C. to 25 C. Any ammonia which vaporizes is allowed to escape. Other procedures also may be used to provide these compositions.

A typical liquid composition of ammonium perchlorate and ammonia is prepared by dissolving these materials in the proportion of 1.519 grams of ammonia per 3.936 grams of high purity ammonium perchlorate at 0 C. to minus 33 C. Thereafter, the resulting composition is allowed to warm to room temperature, about 25 C. A composition containing 70 percent by weight ammonium perchlorate and 30 percent by weight ammonia results.

By limiting the amount of ammonium perchlorate dissolved in the ammonia according to the above procedure, it is possible to provide liquid compositions containing at least 65 weight percent ammonium perchlorate.

The specific impulse for a liquid monopropellant composition containing about percent ammonium perchlorate and 20 percent ammonia as herein described is 234 as calculated for a combustion pressure of 500 pounds per square inch absolute gauge and an exit pressure of 14.7 pounds per square inch absolute in accordance with the procedures outlined in chapter XIV of Chemistry Problems in Jet Propulsion (Penner, S. 5.; Pergamon Press, New York, 1957). This is regarded as a significantly high specific impulse for a monopropellant and indicates the usefulness of the liquid compositions comprising ammonia solutions of ammonium perchlorate wherein the ammonium perchlorate is present in a concentration of at least about 65 percent, and preferably at least about 70 percent and up to about 80 percent by weight. For best results as a propellant, these compositions are essentially anhydrous and contain only ammonia and ammonium perchlorate, except that other oxidants and/or fuels soluble therein may be present, usually for the purpose of having present substantially stoichiometric proportions of oxidant and fuel.

While the invention has been described by reference to specific details of certain embodiments, it is not intended that the invention be construed as limited to such details except insofar as they appear in the appended claims.

We claim:

1. In the propulsion of rocket engine propulsion chambers through space by the introduction of a fuel into a combustion chamber in said rocket engine propulsion chamber, followed by the combustion of said fuel in said combustion chamber and the exhaustion of the resultant gases, the improvement which comprises feeding to the combustion chamber a liquid mixture of ammonium perchlorate dissolved in ammonia, said mixture containing from about 65 percent to about 80 percent by Weight of ammonium perchlorate.

2. A normally liquid propellant comprising a normally liquid mixture of ammonium perchlorate dissolved in ammonia and containing from about 65 percent up to about 80 percent ammonium perchlorate by weight of said mixture.

References Cited in the file of this patent UNITED STATES PATENTS 2,393,594 Davis Jan. 29, 1946 5 FOREIGN PATENTS 655,585 Great Britain July 25, 1951 OTHER REFERENCES Canright': Chemical Engineering Progress, vol. 46, N0. 10 S May 1950, pp. 228-232. 

